Acoustic Wave Touch Detecting Apparatus

1. An acoustic wave contact detecting apparatus comprising: a substrate having a surface along which acoustic waves propagate; a mode converting element; a reflection array for causing the generated acoustic waves to propagate along the surface of the substrate; a detector for detecting changes in the acoustic wave caused by an object contacting the surface of the substrate; and a controller for determining the geometric coordinates of the object; wherein: a diffusing portion for diffusing spurious waves, which are generated accompanying the generation of the acoustic waves, is formed on the substrate, the diffusing portion comprising a plurality of substantially parallel inclined lines, which are densely distributed in the vicinity of an edge of the substrate opposite that at which the mode converting element is provided.

2. An acoustic wave contact detecting apparatus as defined in claim 1 , wherein: the diffusing portion is formed of the same material as that of the substrate.

3. An acoustic wave contact detecting apparatus as defined in claim 1 , wherein: the mode converting elements and the diffusing portion are formed by printing.

4. An acoustic wave contact detecting apparatus as defined in claim 1 , wherein: the mode converting elements and the diffusing portion are formed by etching.